In recent years, in a railroad vehicle using an electric motor as an engine (hereinafter, “electric vehicle”), a brake system often uses an electric brake as a braking unit that decreases the speed of the electric vehicle. When such an electric brake is used in combination with a machine brake, a blending control is necessary that changes over from the electric brake to the machine brake by initiating the application of the machine brake while releasing the electric brake before the electric vehicle is stopped.
In general, a main converter controls the electric brake, while a machine brake controller controls the machine brake. On the other hand, in the case of blending control, the machine brake controller monitors the brake force of the electric brake, and the application of the machine brake is initiated so that the total brake force of the electric brake force and the machine brake force is maintained constant. When the response of the machine brake is slow, the total brake force is not maintained constant due to a delayed initiation of the application of the machine brake force. This makes the deceleration speed unstable, resulting in poor ride comfort.
As one of approaches to solve this problem, there has been proposed a control method of outputting, from the main converter to the machine brake controller, a release notification signal for notifying the release of the electric brake at a slightly higher speed than the releasing speed of the electric brake (for example, see Patent Document 1).
According to the method disclosed in Patent Document 1, the machine brake controller advances the timing to issue an instruction to initiate the application of the machine brake by monitoring the release notification signal, thereby matching the initiation of the application of the machine brake force with the initiation of the release of the electric brake force. That is, according to the conventional method, the release notification signal is output when the speed is slightly higher than the speed for releasing the electric brake (electric-brake releasing speed). Thereafter, when the speed reduces to the electric-brake releasing speed, the release of the electric brake is started.    Patent Document 1: Japanese Patent Application Laid-open No. H8-164857